1. Foreign particulate matter in the atmosphere resulting from combustion processes; a type of lithometeor. When smoke is present, the disk of the sun at sunrise and sunset appears very red, and during the daytime has a reddish tinge. Smoke that has come a great distance from its source, such as from forest fires, usually has a light grayish or bluish color and is evenly distributed in the upper air. See smog, haze. 2. Applied to some types of fog. See sea smoke.